We have been able to make DNA copies from genes of three different rotavirus strains (WA, NCDV and Rh2) by reverse transcribing their genomic RNAs or single stranded RNAs synthesized in vitro from rotavirus particles. Tailing of those DNAs and insertion into PBR 322 plasmid has allowed their cloning into E. coli. The genes from which most of these clones derive have been identified by means of a dot hybridization assay. Clones containing copies of each rotavirus gene (except for genes 10 and 11) have been identified. The sizes of the rotavirus cDNA inserts into the plasmids have been determined for more than half of all the clones obtained (more than 2500). Rotavirus cDNAs that may represent full size copies of genes 5-9 have been identified and their restriction patterns analyzed. Some of them are currently being sequenced in order to obtain knowledge on the amino acid sequences of the proteins they code for and for developing a strategy for insertion into expression vectors.